The World is a very complex system. It is easy to have too simple a view of it, and it is easy to do harm and to make things worse under the impulse to do good and make things better.

There are, of course, a number of epistemological questions, some of which lie more in the province of the philosopher than they do the economist or the social scientist. The one with which I am particularly concerned here is that of the role of knowledge in social systems, both as a product of the past and as a determinant of the future.

It is almost as hard to define mathematics as it is to define economics, and one is tempted to fall back on the famous old definition attributed to Jacob Viner, "Economics is what economists do," and say that mathematics is what mathematicians do. A large part of mathematics deals with the formal relations of quantities or numbers.

Thus we seem to be on the verge of an expansion of welfare economics into something like a social science of ethics and politics: what was intended to be a mere porch to ethics is either the whole house or nothing at all. In so laying down its life welfare economics may be able to contribute some of its insights and analytical methods to a much broader evaluative analysis of the whole social process.

Economic progress means the discovery and application of better ways of doing things to satisfy our wants. The piping of water to a household that previously dragged it from a well, the growing of two blades of grass where one grew before, the development of a power loom that enables one man to weave ten times as much as he could before, the use of steam power and electric power instead of horse or human power - all these things clearly represent economic progress.

It is clear that the building of models is not a purely mechanical process but requires skill of a high order - not merely mathematical skill but a sensitivity to the relative importance of different factors and a critical, almost an artistic, faculty in the selection of behaviour equations which are reasonable, tentative hypotheses in explaining the behaviour of actual economies.

The tourist business is a trap, it is a tained honey; Man clearly should have stayed in bed, and not invented money.